Electronic motor mount with magnetic decoupler

ABSTRACT

A hydraulic mount assembly is disclosed having a partition including a damping decoupler between two hydraulic chambers. One chamber is formed by an elastomeric member and the other by a resilient diaphragm. During dynamic loading of the mount, fluid passes between the two chambers of the mount by moving around an orifice track and/or by bypass around the decoupler causing expansion and contraction of the diaphragm. A magnetic coil is provided adjacent the diaphragm in alignment with the decoupler to supply a controlling magnetic field. The decoupler is made of a magnetic material and is positionally responsive to the variations in the intensity and direction of the controlling magnetic field. By actively controlling the decoupler position in this manner, the dynamic characteristics of the mount are varied. A control circuit with on-board transducers is provided to monitor vehicle operating and road response conditions and modulate the voltage to the magnetic coil for maximum damping effect. The on-board transducers sense selected parameters to indicate unusual conditions for which modulation is required, such as rough engine operation, engine lugging, rough road conditions, sudden turning and/or rapid acceleration/deceleration.

ELECTRONIC MOTOR MOUNT WITH MAGNETIC DECOUPLER

This is a continuation-in-part of U.S. patent application Ser. No.049,787, filed May 15, 1987.

TECHNICAL FIELD

The present invention relates generally to hydraulic mounts forvibration damping and, more particularly, to a hydraulic mount assemblydesigned to provide infinitely variable damping characteristics.

BACKGROUND OF THE INVENTION

A variety of mount assemblies are presently available to isolate vehiclevibrations, such as for automobile and truck engines and transmissions.One of the most popular mounts today is the hydraulic elastomeric mount.Recent improvements in the decoupler mechanism, such as a mount shown inU.S. patent application No. 008,851, filed Jan. 30, 1987 and entitled"Hydraulic-Elastomeric Mount Displacement Decoupler", have providedsignificant improvement in the performance and efficiency of operation.

The hydraulic mount assembly of this prior invention includes areinforced, hollow rubber body that is closed by a resilient diaphragmso as to form a cavity. This cavity is partitioned by a plate into twochambers that are in fluid communication through a relatively largecentral orifice in the plate. The first or primary chamber is formedbetween the orifice plate and the body. The secondary chamber is formedbetween the plate and the diaphragm.

The decoupler is positioned in the orifice of the plate and reciprocatesin response to the vibrations so as to produce small volume changes inthe two chambers. When, for example, the decoupler moves toward thediaphragm, the volume of the primary chamber increases and the volume ofthe secondary chamber decreases. In this way, at certain small vibratoryamplitudes and high frequencies, the major fluid flow is through thedecoupler and undesirable hydraulic damping is eliminated. In effect,this freely floating decoupler is a passive tuning device.

In addition to the large central orifice, a smaller orifice track isprovided, extending around the perimeter of the orifice plate. Each endof the track has one opening; one communicating with the primary chamberand the other to the secondary chamber. The orifice track provides thehydraulic mount assembly with another passive tuning component, and whencombined with the freely floating decoupler provides at least threedistinct dynamic modes of operation. The operating mode is primarilydetermined by the flow of the fluid between the two chambers.

More specifically, small amplitude vibrating inputs, such as from theengine or the like, produce no damping due to decoupling, as describedabove. On the other hand, large amplitude vibrating inputs produce highvelocity fluid flow through the orifice track, and accordingly, a highlevel of damping force and smoothing action. As a third (intermediate)operational mode of the mount, medium amplitude inputs produce lowervelocity fluid flow through the orifice track resulting in the desiredmedium level of damping. In each instance, as the decoupler moves fromone seated position to the other, a relatively limited amount of fluidcan bypass the orifice track by moving around the sides of the decouplerto smooth the transition between the operational modes.

While the three distinct modes of operation provided by the presentproduction hydraulic mounts thus provide generally satisfactoryoperation, they are not sufficient to furnish the desired maximumdamping and noise suppression under all the continuously varyingconditions encountered during vehicle operation. In response to thisneed, one approach is to provide a dynamic system that utilizes apneumatic bladder to engage the diaphragm in such a way as to modulefluid flow into the secondary chamber, as set forth in U.S. patentapplication No. 929,328, now U.S. Pat. No. 4,756,513 filed Nov. 10,1986, entitled "Variable Hydraulic-Elastomeric Assembly".

Specifically, an inflatable bladder is mounted externally and in closeproximity to the diaphragm, so when inflated, the bladder occupies thearea of normal diaphragm expansion. This in effect creates an artificialstiffening of the diaphragm, and in turn adds resistance to the movementof the fluid between the chambers. Thus, operation of the hydraulicmount is variable in response to driving conditions by varying the airpressure inside the bladder. The pressure is controlled by a computer inresponse to transducers mounted on the vehicle. At a maximum bladderinflation, the diaphragm is forced toward the partition and intopositive engagement with the decoupler. In this manner, the decoupler isdisabled and forced into a seated position toward the primary chamber,creating a condition of maximum stiffness in the mount.

Another hydraulic mount assembly in the prior art is disclosed in U.S.Pat. No. 4,583,723 to Ozawa. The movement of a two portion plate betweenthe two chambers is controlled by an electromagnetic coil. This systemprovides either minimum damping by allowing maximum plate movement whenthe coil is de-energized, or maximum damping by restricting the movementwhen energized. Hence, the mount operates as an ON/OFF device, withoutany appreciable intermediate decoupler control. The plate is not allowedto float with a varying degree of restriction, thus substantiallylimiting the modulation capability.

A need is therefore identified for an improved hydraulic mount assemblythat provides for an active or variable control of the dynamiccharacteristics. The dynamic characteristics of the mount can then betuned, either manually or automatically, to provide the most effectiveand efficient damping and noise suppression over the entire range ofexpected operating conditions. It is desirable that vibration/noisecircumstances, and any combination, such as engine lugging, rough roadconditions, sudden turning and/or rapid acceleration or deceleration, becontrolled in a novel and more efficient manner.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to providean improved hydraulic mount assembly overcoming the above-describedlimitations and disadvantages of the prior art limited to passive tuningconcepts.

An additional object of the present invention is to provide a hydraulicmount assembly with active tunable dynamic characteristics.

Another object of the present invention is to provide a hydraulic mountassembly that is infinitely tunable to more efficiently and effectivelyisolate vibrations and suppress noise over the full range of vehicleoperating and road conditions.

Still another object of the present invention is to provide a reliablehydraulic mount assembly of simple construction and that is inexpensiveto build and capable of furnishing infinitely variable dynamiccharacteristics.

A further object of the present invention is to provide a hydraulicmount that allows the dynamic characteristics to be actively controlledby varying the flow of fluid between the two chambers of the mountassembly in response to an all electronic control circuit.

According to the present invention, these objectives are accomplished bycontrolling the bypass fluid flow around the decoupler, so that for agiven vibration of a certain amplitude and frequency, a different amountof fluid is displaced through the orifice track. Thus, the dampingcharacteristics of the assembly may be actively tuned as required formaximum vibration isolation, and consequently a smoother, quieter ride.

Additional objects, advantages, and other novel features of theinvention will be set forth in part in the description that follows andin part will become apparent to those skilled in the art uponexamination of the following or may be learned with the practice of theinvention. The objects and advantages of the invention may be realizedand attained by means of the instrumentalities and combinationsparticularly pointed out in the appended claims.

To achieve the foregoing and other objects, and in accordance with thepurposes of the present invention as described herein, an activelytunable hydraulic mount assembly is provided for damping and isolatingengine and transmission vibrations. The preferred embodiment of themount assembly selected to illustrate the invention employs the basicstructure including the passive tuning, orifice track feature, shown inthe co-pending application, Ser. No. 008,851, referred to above. Inparticular, the mount assembly includes a pair of mounting membersconnected to each other through a hollow elastomeric body of natural orsynthetic rubber. This hollow body is closed by a resilient diaphragm soas to form a cavity for a damping liquid, which may be a commercialengine antifreeze coolant. A partition or plate is provided to dividethe fluid filled cavity into two distinct chambers. The primary chamberis formed between the partition and the interior wall of the hollowbody. The secondary chamber is formed between the partition and theinterior wall of the diaphragm.

The partition further includes a decoupler and an orifice trackconnecting the two chambers. Certain engine vibration forces within thedesign amplitudes and frequencies of the mount produce a contraction ofthe hollow body and primary chamber. Upon contraction (compression), thedecoupler is actuated with some bypass liquid flowing from the primaryto the secondary chamber, and additional liquid flowing around theorifice track. Once the decoupler is in a seated position in thedirection of the fluid flow, fluid communication is limited to thatthrough the orifice track at the designed rate of flow. This enteringliquid causes stretching of the diaphragm, increasing the volume of thesecondary chamber. Then upon reversal of the force, resulting inexpansion of the primary chamber, the stretched diaphragm contractsforcing liquid back to the primary chamber, completing the dampingcycle.

In addition to the above basic structure, the mount assembly of theinvention is characterized by the active tuning concept referred tobriefly above and specifically in the form of a variable control meansfor modulating bypass flow around the decoupler. In this way, the flowof damping liquid between the two chambers may be infinitely varied oradjusted as between the bypass and the full orifice track flow, and thedynamic characteristics of the mount assembly is thus actively tuned tothe particular design parameters desired.

Of particular significance, the control means may be utilized toactively modulate the liquid flow between the chambers in response tothe vibration being produced at any given time under any given vehicleoperating and road conditions. Thus, the mount assembly is not onlyadvantageously infinitely variable, but may be directly responsive tosensing means, such as vehicle mounted transducers, so as to moreefficiently and effectively isolate vibrations. This active controlmeans for the mount of the invention is highly effective over a broaderrange of amplitudes and frequencies than previously attainable.

Preferably, the control of bypass flow through the central orifice, pastthe decoupler, is accomplished by restraining the decoupler fromfloating freely to a seated position within the divider plate. Twoseated positions are provided within the divider plate, with a firstseated position being toward the primary chamber, and a second seatedposition being toward the secondary chamber. A variable force, that maybe pulsed, is preferably applied to the decoupler to induce movementtoward or away from the seated position and opposite to or in thedirection of fluid flow so that the fluid flow through the orifice isactively controlled.

For example, as fluid is forced from the primary to the secondarychamber by vehicle vibrations, the decoupler may be restrained frombeing pushed by the fluid toward the second seated position by inducingit to move by an outside, magnetic force toward the first seatedposition. Thus bypass flow may continue through the central orifice in acontrolled manner, thereby actively controlling the dampingcharacteristics. Of course, if maximum damping stiffness is desired, thevariable force can instead be utilized to seat the decoupler in eitherdirection, completely stopping bypass flow through the central orifice.

The means for applying the variable magnetic force is supplied by anelectric coil, preferably mounted exterior to the hollow cavity, butinside the confines of the mount assembly so as to be fully protected.The coil is preferably fixed on the inside of the mounting memberadjacent the diaphragm so that only the wires to the coil are exposed.

The decoupler is made of a magnetically-responsive material, preferablysteel, with the rim covered with a magnetic rubber or plastic. Thedivider plate is a non-magnetic material, such as aluminum or plastic.The coil is oriented so that the magnetic force produced restrains themagnetic decoupler from floating freely relative to the divider plate,and thereby controls liquid flow. And for more efficiency, a core isadded and the diaphragm is modified so as to locate the former in closeproximity to the decoupler.

The magnetic force intensity is infinitely variable by changing thecontrol voltage supplied to the coil. Hence a small voltage producesminimal restraint of the magnetic decoupler, whereas a large voltageforces the decoupler to one of the seated positions against the orificeplate, completely stopping fluid flow past the decoupler. Of course,when the decoupler is in a seated position with no liquid flowing pastit, the normal damping flow between the chambers still occurs via theorifice track, which yields the maximum stiffness condition of themount.

If the decoupler is magnetized, then the direction of decoupler travelor restraint, toward the first or second seated positions, depends uponthe direction of the magnetic field. By changing the polarity of thecontrol voltage supplied to the coil, the magnetic field can be reversedfrom an attracting mode to a repelling mode, thus providing thebi-directional movement of the decoupler. The appropriate controlvoltage is supplied by a variable voltage source, which is responsive tothe control means. If the decoupler is a steel plate then the directionof decoupler travel is always toward the coil, regardless of thedirection of the magnetic field.

Thus, the fluid flow between the two chambers in response to a givenamplitude and frequency of vibration is altered. As such, the dynamiccharacteristics of the assembly may be actively adjusted or tuned toprovide the desired vibration/noise isolation in response to anyparticular vehicle operating conditions that can be expected to occur,or alternatively, that do occur during operation.

In accordance with another aspect of the present invention, aparticularly advantageous approach is taken to assure that the dynamiccharacteristics of the mount assembly may be efficiently tuned in directresponse to the varying operating and road conditions, that issimultaneously as they are encountered by the vehicle and withoutoperator intervention. Specifically, a control circuit, including amicroprocessor and associated on-board sensors or transducers, isprovided. The transducers sense selected parameters, such as enginevibration amplitude and frequency that change, for example, when theengine is idling, lugging or being rapidly accelerated. The transducersindicate these vibration conditions to the microprocessor that ispreprogrammed to then module the voltage supplied to the coil varyingthe magnetic force intensity and direction. In this way, the position ofthe magnetic decoupler can be varied to control fluid flow between thechambers. For example, a decrease in the magnetic force may produce anincrease in bypass fluid flow while an increase in magnetic forcedecreases such fluid flow. Thus, the dynamic characteristics of theassembly are automatically controlled and actively tuned, providingmaximum damping effect and noise suppression for smoother and quieterengine and/or transmission operation.

Still other objects of the present invention will become apparent tothose skilled in this art from the following description wherein thereis shown and described a preferred embodiment of this invention, simplyby way of illustration of one of the modes best suited to carry out theinvention. As it will be realized, the invention is capable of otherdifferent embodiments and its several details are capable ofmodifications in various, obvious aspects all without departing from theinvention. Accordingly, the drawings and descriptions will be regardedas illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawing incorporated in and forming a part of thespecification illustrates several aspects of the present invention andtogether with the description serves to explain the principles of theinvention.

FIG. 1 is a schematical representation of the control circuit andelectromagnetic coil of the hydraulic mount assembly of the presentinvention.

FIG. 2 is a cross-sectional view of the hydraulic mount assembly withthe decoupler in an intermediate position.

FIG. 3 is a partial cross-sectional view taken along line 3--3 of FIG. 2showing the electromagnetic coil positioned in the mounting member ofthe hydraulic mount.

FIG. 4 is an enlarged cross-sectional view taken along line 4--4 of FIG.2 showing the cavity within the partition where bypass fluid flowsaround the decoupler.

FIG. 5 is a view like FIG. 2 but with a modified electromagnetic coiland diaphragm.

Reference will now be made in detail to the present preferred embodimentof the invention, an example of which is illustrated in the accompanyingdrawing.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made to the drawing showing the improvedhydraulic-elastomeric mount assembly of the present inventionparticularly adapted for mounting an internal combustion engine in avehicle. The dynamic characteristics of the mount assembly may beadjusted or tuned to meet the specific application. As a result, thedesired amplitude control, as well as the coefficient of damping andresulting dynamic rate best suited to isolate a particular set ofvibration conditions, can be obtained.

The mount assembly includes a cast metal mounting member 10 and stampedsheet metal mounting member 12, as shown in FIG. 2. The mounting members10 and 12 each have a pair of studs 14, 16, respectively. These studs14, 16 project outwardly from the mounting members 10, 12 for attachmentrespectively to an engine (not shown) and an engine supporting cradle orframe of a vehicle (not shown).

A hollow elastomeric body 18 interconnects the mounting members 10, 12.The body 18 is constructed of natural or synthetic rubber. Morespecifically, the body 18 may be molded to and about the mounting member10 and includes an embedded stamped sheet metal retainer 20.

The body 18 defines a hollow cavity 22 for receiving a damping liquid,such as commercial engine antifreeze/coolant. Oppositely located voids24 are formed in the body 18 between the mounting member 10 and theretainer 20. These voids 24 provide directional dynamic rate controlwithin the elastomeric body 18 itself and form a part of the dampingliquid cavity 22. As is known in the art, such voids 24 are especiallyuseful in isolating certain internal combustion engine vibrations.

Together, the mounting member 10, elastomeric body 18 and metal retainer20 form a first subassembly or cover of the mount assembly. The retainer20 includes an outwardly projecting collar 26 at its lower periphery.The collar 26 is formed to receive a second subassembly or base. Thebase comprises the mounting member 12 and elastomeric diaphragm 28 ofnatural or synthetic rubber, a partition 30 with the flow orifice and adamping decoupler 32 with a sealing ring 33, described in further detailbelow.

The elastomeric diaphragm 28 includes an annular rim portion 34 havingperipheral groove formed between upper and lower shoulders 38, 40respectively. The shoulders 38, 40 are flexible so as to receive theouter edge of the partition 30. Thus, the partition 30 is sealinglyengaged by the shoulders 38, 40 on opposite sides of the groove.

The mounting member 12 is formed with a collar to receive the rimportion 34 of the diaphragm 28. The collar of the mounting member 12fits within the collar 26 of the retainer 20. As is known in the art,tabs (not shown) may be provided on the collar 26 and bent over toretain the whole mount assembly together.

The elastomeric diaphragm 28 closes the elastomeric body 18 so as toform therewith the closed damping cavity 22. This cavity 22 is dividedby the partition 30 into a primary chamber 46 enclosed by theelastomeric body 18 and a secondary chamber 48 enclosed by the diaphragm28.

The partition 30 is formed of non-magnetic material, such as die castaluminum as shown, or plastic; and includes a pair of plates 50, 52 withmatching peripheries. As shown in FIG. 2, these plates span the cavity22 and cooperate to define an extended damping orifice track 54interconnecting the chamber 46, 48. One opening 56 is provided at theone end of the orifice track 54 in the plate 50 through which theorifice communicates with the primary chamber 46 (see FIG. 2). A similaropening (not shown) is provided in the plate 52 at the opposite end ofthe orifice track 54 for communication between the orifice and thesecondary chamber 48. Thus, the orifice track 54 interconnects thechambers and may be formed to a selected length.

When a vibratory input is provided to the mount assembly, liquid flowsthrough and around the extended orifice track 54. The fluid exchangebetween the primary and secondary chambers 46, 48 produces the passivelytuned damping effect due to the designed resonance of the column ofliquid in the orifice track 54. The increased resistance to flow alongthe orifice and the inertial effects of the liquid column provides thisproven prior art tuning action.

From the above description of the basic mount assembly, it is clear thata passive tuning mode is employed. In our discovery, passive tuning isenhanced by the addition of active tuning of the dampingcharacteristics. Thus, as will be more fully described below, and inaccordance with the broad aspects of the present invention, the overalldynamic characteristics of the mount assembly are actively tuned to dampvibration at any particular amplitude and frequency produced duringvehicle operation. In short, to achieve this result, the bypass flow ofdamping liquid between the two chambers 46, 48 is infinitely varied bycontinuously controlling the position of the decoupler 32, thusregulating the fluid flow around the decoupler to a desired valve.

The hydraulic damping decoupler 32, known in the art and fully describedin the previously referenced co-pending patent applications, takes theform of a rectangular plate. However, to provide active, infinitelyvariable damping, the decoupler 32 of this invention must bemagnetically responsive. That is, it must have a metal component with aferrous content sufficient to move the decoupler in response to anapplied variable magnetic field. The sealing ring 33 is also preferablyformed of a magnetic rubber so as to also be responsive to an appliedmagnetic field. The decoupler 32 is otherwise free floating (see FIGS. 2and 4) since the plates 50, 52 are non-magnetic.

The decoupler 32 is mounted for its limited free floating reciprocalmovement in central orifice 60 (see FIG. 4). The respective upper andlower faces of the decoupler 32 are directly engaged by the dampingliquid within the primary and secondary chamber 46, 48. A first seatedposition is attained when decoupler 32 is forced toward the primarychamber 46 and into positive contact with plate 50, forming aliquid-tight seal. A second seated position is similarly attained whenthe decoupler 32 is forced toward the secondary chamber 48, forming aliquid-tight seal at plate 52. The sealing ring 33 is molded to theperimeter of the decoupler 32, to effect the liquid-tight seal when thedecoupler is in either the first or the second seated position.

Means for applying a variable force are provided to utilize themagnetically responsive characteristic of the decoupler 32 to regulatebypass fluid flow through the central cavity 60 to the desired value.The applying means includes a variable voltage source 80 to supply acontrol voltage, and an electric coil 70, powered by the controlvoltage. The coil 70 is secured to the inside of mounting member 12,just outside the diaphragm 28 and opposite the decoupler 32, as shown inFIGS. 2 and 3. Advantageously, the coil 70 is fully protected with onlythe wire leads 82 extending from inside the mount assembly (see FIG. 3).

The coil 70 is oriented so that a magnetic force produced byenergization of the coil induces the decoupler 32 toward a seatedposition. If the decoupler is magnetized, then whether the decoupler 32is forced toward the first or second seated position will depend uponthe direction of the current flowing through the coil and whether thedecoupler is magnetized. And this will be in accordance with theright-hand rule of electromagnetism. By controlling the direction ofcurrent flow, or in equivalent terms, by changing the polarity of thevoltage applied to the coil, the decoupler is capable of bi-directionalmovement. Choosing the direction of movement of the decoupler within theplates 50, 52 to outward and away from the chamber 46, 48 produces alimited volume change in the chambers that effects hydraulic coupling.

Bypass fluid flow around all sides of the decoupler 32 (note flow arrowsin FIG. 4) is selectively controlled by varying not only the direction,but also the intensity of the magnetic force produced by coil 70. Theintensity of the magnetic force increases with an increase in thecontrol voltage applied to the coil 70. Hence, the decoupler 32 can beeither forced into a seated position at a maximum magnetic force, orvariable restrained from being pushed toward a seated position by fluidflow, as a conventional, free floating decoupler would be.

For more damping effect, the decoupler 32 is restrained from moving fromits normal seated position by the magnetic force, thus reducing thebypass fluid flow and forcing the fluid to flow around the orifice track54. For less damping effect, the decoupler 32 is controlled by theinfinitely variable magnetic force in the opposite direction; that isprevented from moving to and/or staying in the seated position (seeFIGS. 2 and 4). For another mode of operation, the magnetic force isdecreased or turned off all together, to allow the decoupler to morereadily move to the seated position thus allowing the normal, designbypass flow to resume.

The operation of the coil 70 may also be pulsed to provide still anothermode with the bypass fluid volume rapidly changing and in effectcanceling similar undesirable vibrations imposed on the mount. By rapid,bi-directional pulsing, the effects of the decoupler 32 can also beinfinitely varied.

The magnetic force produced by coil 70 may be enhanced by the inclusionof a magnetic core as shown in FIG. 5. This would produce a greatermagnetic force for a given coil voltage, thereby advantageouslyconserving power as described in more detail later.

With the decoupler 32 firmly seated, producing a liquid-tight seal atthe central orifice 60 of partition 30, the only fluid communicationbetween chamber 46 and 48 is via orifice track 54, at the designed rateof flow which yields a condition of maximum stiffness of the mount.

At values of magnetic force less than the maximum, the total fluid flowbetween chamber 46 and 48 is the combination of flow through the orificetrack 54 and through the central orifice 60 of partition 30, arounddecoupler 32. Flow through the orifice track 54 is restricted to aconstant designed rate, whereas bypass flow around the decoupler 32 isvaried by the intensity of the magnetic force. Hence, the total fluidflow is controlled by varying the magnetic force, thereby activelycontrolling the damping characteristics of the mount assembly.

To illustrate the operation of the mount assembly, first assume acompressive force from vibratory action being impressed across mountingmembers 10, 12 producing a contraction of the primary chamber 46. Asthis occurs, the liquid therein is forced to flow into the chamber 48through the orifice track 54 and around the decoupler 32, if themagnetic force is below the maximum value. The chamber 48 then expandsas permitted by the elasticity of the diaphragm 28. On reversal ofvibratory force, that is release of the compressive force, the memory ofthe elastomeric body 18 and the diaphragm 28 causes the primary chamber46 to expand and the stretched diaphragm 28 to retract. The contractionof the secondary chamber 48 forces the damping liquid back through theorifice track 54 and around the decoupler 32 if not seated, and into theprimary chamber 46, completing the damping cycle.

The circuit for controlling the variable voltage source 80 to energizethe coil 70 in precisely the desired manner is shown schematically inFIG. 1. As shown, the coil 70 is connected to variable voltage source 80by wiring leads 82. The variable voltage source 80, which may include arheostat and a switching means for reversing the voltage polarity, isresponsive to a microprocessor 84, through line 86. The microprocessor84 is connected through signal feed lines 88 to a series of transducers90, which form a means for sensing vehicle operating conditions andresulting vibrations. The transducers 90 are mounted on-board thevehicle, such as on the engine and the frame of the vehicle at variouslocations in order to instantaneously sense vibration amplitude andfrequency during operation. To be more specific, transducers 90 may bestrain gauges and positioned in engagement with the engine block andframe (see FIG. 1) adjacent the mount assemblies. These transducers 90are sensitive to the full range of vibratory conditions produced during,for example, idling, rapid acceleration and deceleration, highwaycruising and engine lugging.

The information relative to vibration amplitude and frequency that issensed by the transducer 90 is immediately communication along the lines88 to the microprocessor 84. The information is then processed and apreprogrammed response output signal is communicated along line 86 tothe variable voltage source 80. Specifically, the voltage to the coil 70is modulated and either increased, decreased, and/or reversed inpolarity as required, producing the most effective damping and isolationof engine vibrations for the smoothest possible ride.

The coil voltage is decreased or turned off by the microprocessor 84 inresponse to low vibration frequencies and amplitudes sensed by thetransducers 90, such as during engine idling. This produces acorresponding reduction in the magnetic force, which allows an increasein the designed reciprocating motion of the decoupler and theaccompanying designed bypass fluid flow around decoupler 32 to providethe smooth transition in damping action. Thus, in a no-voltage orminimum voltage state of the voltage source 80, the mount assemblyexhibits relatively soft damping qualities to isolate the lowfrequency/small amplitude vibrations.

When, for example, the engine is then accelerated rapidly from idle, thefrequency and amplitude of engine vibrations are increased. Themicroprocessor 84 processes the information and sends a response signalto the variable voltage source 80 to increase the voltage to the coil70. This voltage increase produces a corresponding increase in themagnetic force, which selectively controls the decoupler 32 so as tomove readily to a seated position and force the fluid around the orificetrack 54. The bypass fluid moving around the decoupler 32 is reduced. Asa result, the mount assembly exhibits relatively stiffer qualities thanexhibited during engine idling. The mount assembly provides increaseddamping characteristics for accommodating vibration of increaseamplitude.

During certain other operating conditions, such as under hard corneringor engine lugging, the mount assembly also exhibits peak damping levelsat high amplitudes and low frequencies. Upon sensing such conditions,the microprocessor 84 directs the variable voltage source 80 to againmomentarily increase the magnetic force to a maximum value. This forcesthe decoupler 32 into a seated position, completely sealing the centralorifice 60 of partition 30. In this operational mode, the mount assemblyexhibits the stiffest qualities. Fluid flow between the chambers 46, 48is substantially limited to that through the orifice track 54, producinga large damping effect at the high amplitudes and low frequencies.

Of course, in between the three conditions described above are aninfinite number of control variations, so that in effect the restrictionof the fluid flow between the chamber 46, 48 is infinitely variable.This feature of active control allows the mount assembly of theinvention to respond to virtually all conditions of vibrations thatmight be encountered for maximum damping action.

In summary, numerous benefits result from employing the concepts of thepresent invention. The hydraulic mount assembly incorporates amagnetically-responsive decoupler 32 that acts in cooperation with avariable magnetic force supplied by coil 70. The variable magnetic forceis applied to either restrain the decoupler 32 from being pushed towarda seated position by fluid forces, or to force the decoupler 32 into aseated position, completely restricting bypass fluid flow around thedecoupler. When the decoupler is firmly seated by a maximum magneticforce, fluid flow between the primary chamber 46 and the second chamber48 is limited to that through the orifice track 54, providing a maximumstiffness for the mount. Specifically, by modulating the voltagesupplied to the coil 70, the damping characteristic of the assembly soactively tuned so as to best dampen troublesome vibrations occurringduring any particular operating conditions. The transducers 90 may beprovided to instantaneously sense the amplitude and frequency ofvibrations being produced at any given time. The preprogrammedmicroprocessor 84 is provided to instantaneously process the informationfrom the transducers 90. The microprocessor 84 in turn operates avariable voltage source 80 to modulate the magnetic force produced bycoil 70, automatically yielding the most effective and efficient dampingand vibration isolation.

Moreover, the efficiency of the magnetic action on the decoupler can besignificantly improved where desired by the addition of a core andmodification of the diaphragm as shown in the embodiment in FIG. 5wherein the same numerals are used to identify previously describedparts and new numerals are used to identify the added and modifiedparts. In the FIG. 5 embodiment, a cylindrical iron core 100 is mountedcentrally of the coil 70 with its base 102 fixed to the mounting member12. The core extends upwardly substantially beyond the coil so that itsupper end 104 is located in close proximity to the decoupler 32 aspermitted by an accommodating cavity 106 now formed in the diaphragm 28centrally thereof directly beneath the decoupler. As a result, the gapin the magnetic field is substantially reduced so that less magneticforce need be generated to control the decoupler action.

The foregoing description of the preferred embodiment of the inventionhave been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Obvious modifications or variations are possible inlight of the above teachings. The embodiments were chosen and describedto provide the best illustration of the principles of the invention andits practical application to thereby enable one of ordinary skill in theart to utilize the invention in various embodiments and with variousmodifications as is suited to the particular use contemplated. All suchmodifications and variations are within the scope of the invention asdetermined by the appended claims when interpreted in accordance withbreadth to which they are fairly, legally and equitably entitled.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A hydraulic mountassembly providing variable damping characteristics, comprising:a pairof mounting members; a hollow body connected to said mounting members; aresilient diaphragm closing said hollow body forming therewith a closedcavity that is filled with liquid; partitioning means for partitioningsaid cavity into a primary chamber and a secondary chamber enclosed bysaid diaphragm; an elongated damping orifice extending about and throughsaid partitioning means between said chambers so as to effectsubstantial restricted liquid flow between said chambers and therebydamping; a decoupler mounted for limited free floating reciprocalmovement in a bypass orifice through said partitioning means between theprimary and secondary chambers with a first seated position toward theprimary chamber and a secondary seated position toward to secondarychamber to restrict and control liquid flow between said chambers inbypass relation to said damping orifice so as to effect damping control;sensing means for sensing vehicle operating conditions and resultingvibrations; external decoupler control force means for applying avariable force across the liquid in said secondary chamber and saiddiaphragm effective to induce said decoupler toward one of said seatedpositions whereby liquid flow around said decoupler is infinitelyvariable; and means for controlling the variable force in response tosaid sensing means for sensing vehicle operating conditions so as toallow the damping characteristics of said mount assembly to be tuned;said external decoupler control force means for applying a variableforce including a variable voltage source responsive to said controllingmeans to produce a control voltage; and an electrical coil mountedexterior and adjacent to said diaphragm to produce a variable magneticforce in response to the control voltage; and said decoupler includingmagnetic material so as to be magnetically responsive across the liquidin said secondary chamber and said diaphragm to the variable magneticforce whereby the mount assembly damping characteristics are activelytuned, said diaphragm having a cavity in the exterior thereof with abottom in close proximity to said decoupler, a core mounted in andextending beyond said coil into said diaphragm cavity to said bottomthereby to be located in close proximity to said decoupler.